What’s the Difference Between Whey, Soy, and Pea Protein?

by Sean Hyson

“What’s the difference between whey, soy, and pea protein? Which one is best?” —Martin B., New York, NY

Whey protein, made from milk, has the most research behind it, and it’s widely accepted as a top supplement for building muscle. If I had to pick the “best” protein out there, whey would be the one. That said, it isn’t an option for some people with certain diet restrictions.

Soy protein isolate offers similar speed of absorption to whey and all the essential amino acids (a rarity for a non-animal protein source). However, a 2013 study in the Journal of the American College of Nutrition compared the effects of supplementing with whey versus soy and found that subjects using soy had “lower testosterone responses.” In addition, the whey users were better able to blunt cortisol (a stress hormone that breaks down muscle).

Pea protein, then, is perhaps a better option than soy. It comes from yellow peas and, like soy, is complete (it contains all the essential amino acids). Pea protein is also allergen free, making it good for those who can’t digest whey, but the research behind it isn’t as strong as that of whey and soy.

It comes down to preference. The protein you choose should be one you enjoy the taste of and that fits your budget, lifestyle, and goals.

Sean Hyson, C.S.C.S., is the Men’s Fitness training director and author of 101 Best Workouts of All Time (101bestworkouts.com).